Optical disc drive apparatus, method of controlling the position of optical pickup unit, method for detecting an device for reading and/or writing of a disc

ABSTRACT

Device for reading of and/or writing on a disc. The device is provided with at least one shaft ( 2, 3 ) and a carrier ( 10 ) movable along said shaft. The carrier is provided with at least one actuator ( 14 ) which is electrically connected to a control device ( 16 ). The actuator is electrically connected to said control device by means of said shaft.

The invention relates to a device for reading and/or writing of a disc,which device is provided with at least one shaft extending along acenterline and a carrier which is displaceable over said shaft and isprovided with at least one actuator, said actuator being electricallyconnected to a control device.

Such a device known from American patent application US-A1-2002/0021631is suitable for use in a Compact Disc (CD) or Digital Video Disc (DVD),whereby optical discs can be read and/or written. For this purpose, alens is controlled by the actuator such that a laser beam can beradially corrected by means of the lens and can be focused, so that thelaser beam is positioned in a desired location of the disc, and the discas a result can be read and/or written. The actuator is controlled by acontrol device. To keep the weight of the carrier as low as possible,the control device will usually be arranged in the solid world. Thecontrol device arranged in the solid world is electrically connected tothe actuator.

A disadvantage of such a known device is that the electrical connectionbetween the actuator and the control device located in the solid worldis achieved by means of a cable connection, which cable connectionoccupies comparatively much space. A further disadvantage of a cableconnection between the control device and the actuator is that the cableconnection may intercept the laser beam.

It is an object of the present invention to provide a device in whichthe actuator is electrically connected to the control device in a simplemanner.

This object is achieved in the device according to the invention in thatthe actuator is electrically connected to the control device by means ofsaid shaft.

The shaft of the device according to the present invention thus has adual function: firstly, the shaft serves as a mechanical guide for thecarrier that is displaceable over the shaft, and secondly, the shaftprovides an electrical conduction between the actuator situated on thecarrier and the control device in the solid world. An advantage of thisis that the electrical connection between the actuator and the controldevice occupies substantially no additional space and cannot cause anyinterception of the laser beam.

An embodiment of the device according to the invention is characterizedin that the carrier is displaceably supported with respect to the shaftby means of at least one bearing, while the actuator is connected to theshaft with electrical conduction via said bearing.

The bearing provides both a good mechanical guide and a good electricalconduction.

An alternative embodiment of the device according to the invention ischaracterized in that the bearing is connected to the shaft withelectrical conduction under spring force.

An advantage of such an embodiment is that the bearing can slide overthe shaft with comparatively low friction, while at the same time thebearing makes electrical contact with the shaft in a simple manner.

A yet further embodiment of the device according to the invention ischaracterized in that the actuator is connected to the shaft withelectrical conduction through the carrier.

The connection between the shaft and the actuator can also be realizedwithout loose cables in this manner.

A further embodiment of the device according to the invention ischaracterized in that the shaft comprises at least two shaft segmentswhich are electrically separated from one another.

Such an embodiment has the advantage that a different control signal canbe sent from the control device to the actuator through each shaftsegment.

A still further embodiment of the device according to the invention ischaracterized in that the bearing comprises at least two bearingsegments which are electrically separated from one another, eachelectrically conductive bearing segment of the bearing being in contactwith an associated shaft segment of the shaft.

An advantage of such an embodiment is that such a construction of thebearing corresponding to that of the shaft achieves an electricalcontact between the control device and the actuator in which thedifferent control signals can be passed on in a simple manner.

A yet different embodiment of the device according to the invention ischaracterized in that the bearing segments and shaft segments extendparallel to the centerline.

Such an embodiment has the advantage that a good electrical connectionis safeguarded over the full length of the shaft in a simple manner.

A yet further embodiment of the device according to the invention ischaracterized in that a lens can be positioned by means of the actuator.

The lens can be accurately positioned by means of the electricalconnection via the shaft between the control device and the actuator.

The invention will be explained in more detail by way of example withreference to the accompanying drawings, in which:

FIG. 1 is a perspective view from above of a device according to theinvention, and

FIG. 2 is a cross-sectional view on an enlarged scale of a guide elementand a bearing of the device shown in FIG. 1.

Corresponding components have been given the same reference numerals inthe Figures.

FIG. 1 shows a device 1 according to the present invention which issuitable for reading and/or writing of, for example, an optical disc(not shown), such as a Compact Disc (CD) or Digital Video Disc (DVD).The device 1 is provided with two shafts 2, 3 which are mutuallyparallel. The shafts 2, 3 are each provided with two shaft segments 4, 5and 6, 7, respectively, which extend parallel to the centerline of theshaft 2, 3. The shaft segments 4, 5 and 6, 7 are separated by respectiveinsulation layers 8, 9 which extend over the full lengths of the shafts.A carrier 10 is supported between the shafts 2, 3 by three bearings 11,12, 13, such that the three bearings 11, 12, 13 have a sufficientmechanical stability and experience as little friction as possibleduring the mechanical displacement over the shafts 2, 3. An actuator 14capable of controlling a lens 15 in and opposed to directions indicatedby arrows X, Y, and Z is present on the carrier 10. The electricalconnection between the actuator 14 and respective shaft segments 4, 5and 6, 7 is achieved through the electrically conductive bearings 11,13, as will be explained in more detail with reference to FIG. 2. Acontrol device 16 is connected to the actuator 14 situated on thecarrier 10 via two electrical circuits 16, 18. The electrical circuits17, 18 extend from the control device 16 through the respective shaftsegments 4, 5 and 6, 7 and the electrically conductive bearings 11 and13 via the carrier 10 to the actuator 14. A signal can be sent to theactuator 14 through each of the electrical circuits 17 and 18.

A connecting rod 19 is situated between two bearings 11, 12 provided onthe shaft 2, which rod is connected to a drive means 20 by which thecarrier 10 can be displaced in and opposed to the direction indicated byarrow X.

FIG. 2 is an enlarged cross-section of the shaft 2 and the bearing 11 ofthe device 1. The bearing 11 is provided with two electricallyconductive bearing segments 25, 26 which are mutually separated by aninsulating layer 27. The electrically conductive bearing segments 25, 26are connected to the shaft 2 with electrical conduction via springs 28,29, 30, 31 and sliding contact plates 32, 33.

The operation of the device 1 will now be briefly explained. If a discextending parallel to the shafts 2, 3 is to be read and/or written, alaser beam 35 must be accurately aimed at the disc. To achieve acomparatively large displacement of the carrier 10 and the actuator 14and lens 15 situated thereon with respect to the disc, the carrier 10 isdisplaced by the drive means 20 in and opposed to the directionindicated by arrow X over the shafts 2, 3. The lens 15 is displacedrelative to the carrier 10 by the actuator 14 to achieve a comparativelysmall displacement necessary for a focusing and radial positioning of alaser beam 35 originating from a laser (not shown). The actuator 14 iscontrolled by the control device 16 for this purpose. A radialdisplacement of the lens 15 in and opposed to the direction indicated byarrow X is controlled via the electrical circuit 17, and focusing of thelens 15 in and opposed to the direction indicated by arrow Z iscontrolled via the electrical circuit 18. Corrections in the Y-directiontake place through rotation of the disc to be read or written.

It is possible to have more than one signal pass through the shafts 2, 3in that the shaft is subdivided into a plurality of shaft segmentsobtained by means of a plurality of insulation layers. The bearingshould then be adapted accordingly.

Carbon brushes may alternatively be used as sliding contact surfaces forthe electrical conduction between the contact faces of the electricalbearing and the shaft.

1. A device for reading and/or writing of a disc, which device isprovided with at least one shaft extending along a centerline and acarrier which is displaceable over said shaft and is provided with atleast one actuator, said actuator being electrically connected to acontrol device, characterized in that the actuator is electricallyconnected to the control device by means of said shaft.
 2. A device asclaimed in claim 1, characterized in that the carrier is displaceablysupported with respect to the shaft by means of at least one bearing,while the actuator is connected to the shaft with electrical conductionvia said bearing.
 3. A device as claimed in claim 2, characterized inthat the bearing is connected to the shaft with electrical conductionunder spring force.
 4. A device as claimed in claim 1, characterized inthat the actuator is connected to the shaft with electrical conductionthrough the carrier.
 5. A device as claimed in claim 2, characterized inthat the shaft comprises at least two shaft segments which areelectrically separated from one another.
 6. A device as claimed in claim5, characterized in that the bearing comprises at least two bearingsegments which are electrically separated from one another, eachelectrically conductive bearing segment of the bearing being in contactwith an associated shaft segment of the shaft.
 7. A device as claimed inclaim 6, characterized in that the bearing segments and shaft segmentsextend parallel to the centerline.
 8. A device as claimed in claim 1,characterized in that a lens can be positioned by means of the actuator.